Chemical warfare agents are toxic compounds showing negative effects on living organisms. This review focuses on detection of nerve and blister agents, which are two most important classes of chemical warfare agents. Main attention is paid to the construction and use of biosensors. Acetylcholinesterase, butyrylcholinesterase and phosphotriesterase are presented as convenient biorecognition components of biosensors for detection of nerve agents, while dehalogenases are useful for detection of mustard agents.